In electromagnetic actuators for actuating the gas-exchange valves of an internal combustion, there is a need to achieve high switching speeds and at the same time high switching forces. These actuators essentially comprise an armature, which is connected to a gas-exchange valve to be actuated and is guided to reciprocate counter to the force of two oppositely oriented restoring springs between the pole faces of two spaced-apart electromagnets. The electromagnets have a current supply which is controllable via a control device and act as opening and closing devices. For actuating the gas-exchange valve from one position, for instance the closing position, to the other, in this case the opening position, the holding current at the holding electromagnet is turned off. This causes the holding force of the magnet to drop below the spring force, and the armature begins to move, accelerated by the spring force. Once the armature has passed through its position of repose, the "flight" of the armature is braked by the spring force of the opposed restoring spring. In order now to intercept the armature in the opening position and hold it there, the corresponding magnet is supplied with current. In this interception process, the problem arises that the requisite induction of force by the magnet depends on numerous parameters. For instance, depending on the current engine load, the braking of the gas-exchange valve by gas forces, particular for the outlet valve, is highly variable. Moreover, the energy required for the interception is subject to influence by mass-production variations and from wear. Correspondingly, the "correct" energy supply for proper operation is quite important. If the energy supplied to the intercepting electromagnet is too high, then because of the overly high impact speed, severe wear occurs along with an unacceptable noise level. Under unfavorable circumstances, The armature can even bounce away again and thus put the valve out of operation for this stroke. If the energy supplied to the intercepting electromagnet is too low, then the armature is not intercepted, and the gas-exchange valve swings back again, so that at least in this cylinder cycle proper operation will not occur.
To overcome these problems, the attempt has already been made to reduce the impact speed of the armature by providing buffers comprising damping materials. However, problems of wear that could hardly be solved resulted.
The attempt was also made to solve the problem by providing air damping, as described in German Patent Disclosure DE-A 38 26 974. The disposition of an air damper presents engineering problems upon conversion to mass production. Particularly the construction of rectangular armature cross sections presents considerable problems in this respect. Moreover, energy losses that can longer be ignored result. In both known attempts to solve these problems, the disadvantage also exists that adaptation to changing operating parameters or wear factors is impossible.